The journal of the Center for Bead Research Volume 11, Number 1 Issue 25 1998 (10(2) GLASS , . , A diagram of the structure of a crystalline substance (on the left) and of glass (on the right). The·black dots are silicon, the open dots oxygen and • the shaded dots sodium (after Brill 1962:133). GLASS ANALYSIS Fig. 2 Glass factory of the 16 century from Biringuccids Pyrotechnia (Smith. and Gnudi 1943: 133). and t~e Al:'fALYSIS OF INDO-PACIFIC BEADS ~. The MARGARETOLOGIST is published twice a year with the most current information on bead researc~ primarily our O"TI. USA: Members: 53012 y~ats, Patrons: 580/2 years, Supporters: 520012 years, Foreign: 535. 590. $210. Upp<rr ltlvels receive more privileges. Entire COTltedtS © 1998 Peter Francis. Jr. Reproduction forbidden in any fOIin without written jXTTIlission ISSN 08921 989 Center for Bead Rc:search, 4 Essex: St., Lake Placid, NY 12946·1236 'Phone (518) 523·1794 E-mail pfjr@norlhn.:t.org·Website:w\\w.tht:!J..:adsittl.com The Margaretoro'gist Vol. 11, No.1 Issue 25 199~ The, last year has been exciting. It inc1uded=>;> 15-19 June: Consulting at· American e· appearances in Toronto, Denver, Chicago Museum of Natural History•.!'JYC,St. ,'and Mitineapolis,a most satisfying Bead Catherine's' GA. Expo '98 and continuing consulting with =>' 19 October,... 5 November: Bead and' Art Tour of India; stay in India formore re- the Americah Museum of Natural History, search . New York on St. Catherines, ·Georgia. I<~!{~~fg~t1~;~r,~~B~~¥~l§.!R1'1;Mlt.f was in Ghana for three months and on to Send us your email address. , the Berenike, Egypt, excavation for one. I ..J If the last digits on your mailing label got very sick the last month in Ghana and are 11:1, it's time to renew. remained so in Egypt. I have slowly recov­ ..J Notify us of any address changes ered since (the doctors never did figure out ..J Each classotmembership receives free what it was). Thanks to all who expressed advertising space and free Bead Identifi­ cation Certificates or Research Reports their concerns. I am much better now. ..J Memberships make wonderful presents A highlight of this year has been the -V Encourage your Bead Society, shop or analyses of20Indo-Pacific bead samples by institution to support us and allbeadre­ Ron Hancock ofthe University of Toronto, . search groups ' . to whom I am deeply grateful. This pro­ © , . The Margret. Carey "Gotcha" Award has gram has answered several questions re­ been extended to The Bead Site. She wins garding this crucial bead industry, It is the . again. Corrections for'10(2). key finding presented in this issue: To in~ Page/Column/Paragraph/line troduce it, I enlarged on the topics of glass 211/2/4 identify to identity and glass analyses. I hope you find it 41213112 cassock to hassock stimulating. 6/112/2 bead to beads . 71113/8 em to rum The last issue (Seed Beads) has been one 91112/4 beads to bead . • of the best-received numbers to date, This 10/2/3/3 ordian:ry to ordinary is due to the tremendous interest in beading ll/1/3/6 color lined to color-lined and the desire to understand the complexi­ 13/11512 Libraire to Librairie. ties of the smallest beads. The success of 14/11117 Indonesia to Indonesia, Bead Expo '98 and the popularity of the Seed Bead Gallery on the thebeadsite.com are further proof ofthis, ifany is needed, Our web site, thebeadsite.com, just keeps b'ooming. Because of it, I can present all the analyses made of Indo-Pacific beads (this issue has the new ones in Table 2). To access them go to www.thebeadsite.com. F rom the home page go to Galleries, then to Color Plates for the Margaretologist, then to the version appropriate for your browser. Ifyou absolutely can '/ get ~n the;Ai1}.;: . 'Ut3:'t:eCdiri1Ortab1e}/ "";') Internet and absolutely must have copIes of ··:J~~t;ei;~;;n~};~~tifeEfeai:la;;d A# " these tables, .let m_~ ~ow"TotJr oflncfj8.CfO!$jrig.'deadll~'iih$fic1n . Happy surfing! mi·"See' ril()l'eat.~:ttle~ad~ite;com/ .' 2 The Margaretologist Vol. 11J No.1 Issue 25 1998 Glass and Glass Analysis • The world Just wouldn't be the same with- . sometimes called an "under-cooled" liq­ out glass .. There, would be no windows, uid. Additionally, glass does not have a bottles or porcelam bathroom fixtures, not definite meltino- point. It becomes more to mention televisions or light bulbs. And or less viscouso slowly, without a sudden where wo~ld beads be? change in phase at a precise temperature. Glass .IS so commonplace that we call The American Society for Testing and m~ny objects by that name spectacles, Materials (1979:294-5) defines glass as: mmors, laupes and tumblers. Yet the An inorganic product of fusion which has nature of glass is a matter of scientific de- cooled to arigid condition without crystallizing. bate and hardly perceived by most people. Glas~ is typically hard and brittle and has a Glass is an odd duck. It is not a strictI conchCOlda1 fracture. It may be colorless or col­ . y ored, and transparent to opaque. Masses or bodies ma~enal: b~t a state of matter, on par with of glass may be made colored, transparent, or solIds, lIqUIds, gasses and plasmas. It is opaque bythe presence of dissolved, amorphous or similar to solids because it is firm, but crystalline material. ' also to liquids, because it lacks a crystal"' Many solids can be made glassy if line structure (Fig. 1). melted and cooled quickly enough to pre­ Let's compare o-lass to more common vent recrystallization. Since the 1960s, states of matter, u~ng water as an exam- metal~ic glasses have become important pie. 'When the temperature is over 100° C matenals. Razor blades and tape recorder water is a gas called steam. The H20 heads were early uses, and other applica­ molecules are very excited (have high ki- tions are being developed rapidly, netic energy), move around rapidly and The precise structure of glass is under • fill any container. When the temperature de?ate. Some liken it to polymers (lo.ng drops below that point steam condenses stnngs of molecules) that charactenze into a liquid and gathers at the bottom of a plastics. Others believe it is composed of container, filling only a discrete volume. submicroscopic distorted crystals that The molecules still have considerable ki- form a random lattice. It can be thought netic energy and slip and slide around of a~ an irregular network tha~ can enclose each other. Water is not very viscous foreign atoms or molecules (FIg. 1). (heavyweight oil and molasses are more In everyday speech, and from hereon in viscous), so it flows easily. this issue, the word "glass" is not used to When the temperature drops below 0° desi~nate a ~ate of matter ?ut to refe~ to.a C. water forms ice crystals. The mole- partIcular rruxture of OXIdes. This IS. cules are bound to too-ether and no longer "commercial glass," the glass of everyday move around. 1 Ice is rigid; it is a solid. experience, Glass is firm, but highly viscous rather than strictly rigid. It has no crystalline The Glassmaking Oxides structure but a lattice or network of mole­ Glass is usually composed of three types cules. It is thus like a liquid, but for prac­ of oxides, elements combined with oxy­ tical purposes resembles a solid. It is gen, the most common molecules. Some are called simply iron oxide or lead oxide. Several are'named by changing the ending 1 TIleir kinetic energy now only" allows them to '" of the element to -a or -ia. Thus, the ox ­ vibrate', as do all substances until absolute zero (ca. ide of silicon is silica, of aluminum alu­ '. -273° C) is reached. 3 The Margaretologist Vol. 11, No.1 Issue 25 1998 mina, of sodium soda and so on. Some Fig. 3 (adapted from Scholes ~nd Greene have special names -- potash for petas;.. 1975:38) gives an idea ofthese properties. sium oxide and lime for calcium oxide. The three major irigredients of soda-lime . Some oxides are "network fonners" that glass are drawn at 1200 to each Other. At " • create glass b:r themselves. They have the lower right, silica- gives' glass its vis­ atoms surrounded by four oxygen atoms cosity and vitreous character' and retards and can fonn chains and networks in ran­ its expansion under heat. To;·the lower" dom fashion. Of these, silicon is by far left, soda lessens viscosity, l promotes": the most important. Next to oxygen, sili­ thermal expansion and makes glass prone' con is the most common element in the to attack by water. At the top, lime pre­ Earth's crust, accounting for 27.6% of the vents solubility in water and contributes to atoms and 59% of its weight. Boron is the the tendency to crystallize, ot 'devitrify. other important network former. Other gIassmaking oxides are arranged in A second group of oxides are "network approximate relative positions:' As the modifiers." The central atoms are larger original authors noted, this 'scheme is than those of network fonners and must oversimplified since no clear-cut division be surrounded by more oxygen atoms. between the ingredients can be drawn. They do not become glassy by them­ Yet is it a useful schematic representation selves. but when melted with network ofthe origins of properties. formers enter the glass composition. They include such critical ingredients as soda, Devitrffication • 0",0 ("'0 MJO .